yoToco94 :
But what does the RAM do in terms of graphics?
RAM on a graphics card is just like the RAM in your computer. Information is sent and stored there that will need to be accessed much quicker than it can access on a hard drive. Theoretically the more RAM the better, but you need processing power to utilize that RAM. From my experience, to have 6GB of RAM on a GPU beneficial would be to liquid cool your graphics card and overclock it like no other. I have a GTX 680 stock running at 1084MHz and it doesn't even utilize all the 2GB of RAM. Now if I were to overclock it quite a bit, then my 2GB of RAM would start to bottleneck the processor speeds of my graphics card.
So the question becomes, do you plan to overclock the card? If you do, you better have a liquid cooling set up planned. Because there will be no way you'll get it cool enough to utilize that much RAM. If you don't plan to liquid cool, and just plan to keep the cards at stock speeds. The 3GB card is more than enough RAM.